This invention relates in general to the production of foamed material and more particularly to an apparatus for casting a foam so that the top surface thereof as well as the bottom and sides have a desired contour.
Foamed synthetic resins such as polyurethane find wide-spread use in a variety of products where cushioning properties are desired. For example, the back and seat cushions of much of the furniture produced today contain foamed or cellular polyurethane, as do many automobile seats. The foam material is initially cast in elongated buns, and in the more advanced processes the casting is continuous. In one process which is widely used, the mold consists of a long strip of paper which is folded into a three-sided configuration and is drawn through a trough. A liquid reaction mixture is poured onto the bottom wall of the paper mold and as the mold continues to move, the reaction mixture expands into a foam or bun which is confined by the paper mold. This rise of the foam at the sidewalls of the mold is less than at the center of the mold, due to the friction between the sidewalls and the foam and the tendency of the foam to adhere to those sidewalls. As a result, the foam or bun acquires a convex top surface, commonly referred to as a crown. Also, the liquid reaction mixture tends to remain confined in a channel in the center of the mold and this compounds the tendency of the foam or bun to acquire greater height at its center. Since the greatest demand for foam material is for that possessing a rectangular configuration, the convex top is usually cut off. This requires an additional operation in the process and furthermore the material cut-off constitutes waste.
The continuous casting process has heretofore been used only for producing foam material with flat bottoms and squared off sidewalls and has never been used to create buns of different configurations.